What is the atmospheric pressure gauge pressure and absolute pressure and relation between them?

Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere, typically measured at sea level and approximately equal to 101.3 kPa (kilopascals) or 1 atm. Gauge pressure is the pressure measured relative to atmospheric pressure, meaning it excludes atmospheric pressure from its measurement; it can be positive or negative depending on whether the pressure is above or below atmospheric pressure. Absolute pressure, on the other hand, is the total pressure measured relative to a perfect vacuum, and is calculated by adding atmospheric pressure to gauge pressure. The relationship can be expressed as: Absolute Pressure = Gauge Pressure + Atmospheric Pressure.